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Diffstat (limited to 'contrib/e1-prbs-test/prbs.c')
| -rw-r--r-- | contrib/e1-prbs-test/prbs.c | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/contrib/e1-prbs-test/prbs.c b/contrib/e1-prbs-test/prbs.c new file mode 100644 index 0000000..ed8a80a --- /dev/null +++ b/contrib/e1-prbs-test/prbs.c @@ -0,0 +1,183 @@ +/* (C) 2019 by Harald Welte <laforge@gnumonks.org> + * All Rights Reserved + * + * SPDX-License-Identifier: GPL-2.0-or-later + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published + * by the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <stdint.h> +#include <string.h> +#include <osmocom/core/utils.h> +#include <osmocom/core/prbs.h> + +#include "internal.h" + +/* according to https://users.ece.cmu.edu/~koopman/lfsr/index.html all below + * coefficients should render maximal length LFSRs of 11bit (2048) length */ +static const uint32_t prbs11_coeff[] = { + 0x402, + 0x40B, + 0x415, + 0x416, + 0x423, + 0x431, + 0x432, + 0x438, + 0x43D, + 0x446, + 0x44A, + 0x44F, + 0x454, + 0x458, + 0x467, + 0x468, + 0x470, + 0x473, + 0x475, + 0x47A, + 0x486, + 0x489, + 0x492, + 0x494, + 0x49D, + 0x49E, + 0x4A2, + 0x4A4, + 0x4A8, + 0x4AD, + 0x4B9, + 0x4BA, + 0x4BF, + 0x4C1, + 0x4C7, + 0x4D5, + 0x4D6, + 0x4DC, + 0x4E3, + 0x4EC, + 0x4F2, + 0x4FB, + 0x500, + 0x503, + 0x509, + 0x50A, + 0x514, + 0x524, + 0x530, + 0x536, + 0x53C, + 0x53F, + 0x542, + 0x548, + 0x54E, + 0x553, + 0x555, + 0x559, + 0x55A, + 0x56A, + 0x56F, + 0x574, + 0x577, + 0x578, + 0x57D, + 0x581, + 0x584, + 0x588, + 0x599, + 0x59F, + 0x5A0, + 0x5A5, + 0x5AC, + 0x5AF, + 0x5B2, + 0x5B7, + 0x5BE, + 0x5C3, + 0x5C5, + 0x5C9, + 0x5CA, + 0x5D7, + 0x5DB, + 0x5DE, + 0x5E4, + 0x5ED, + 0x5EE, + 0x5F3, + 0x5F6, + 0x605, + 0x606, + 0x60C, + 0x60F, + 0x62B, + 0x630, + 0x635, + 0x639, + 0x642, + 0x644, + 0x64B +}; + +/* build the PRBS description for a given timeslot number */ +void prbs_for_ts_nr(struct osmo_prbs *prbs, uint8_t ts_nr) +{ + + OSMO_ASSERT(ts_nr < ARRAY_SIZE(prbs11_coeff)); + prbs->name = "custom"; + prbs->len = 11; + prbs->coeff = prbs11_coeff[ts_nr]; +} + +/* compute one full sequence of the given PRBS */ +void prbs_precomp(struct prbs_precomp *out, const struct osmo_prbs *prbs) +{ + struct osmo_prbs_state prbs_s; + int i; + + osmo_prbs_state_init(&prbs_s, prbs); + for (i = 0; i < sizeof(out->bytes); i++) { + ubit_t ubit[8]; + osmo_prbs_get_ubits(ubit, sizeof(ubit), &prbs_s); + osmo_ubit2pbit(&out->bytes[i], ubit, sizeof(ubit)); + } +} + +void ts_init_prbs_tx(struct timeslot_state *ts, unsigned int prbs_offs_tx) +{ + unsigned int prbs_nr = prbs_offs_tx + ts->ofd.priv_nr; + /* initialize the transmit-side PRNG for this slot */ + printf("Selecting PRBS11 #%02u for Tx of TS%02u\n", prbs_nr, ts->ofd.priv_nr); + prbs_for_ts_nr(&ts->tx.prbs, prbs_nr); + prbs_precomp(&ts->tx.prbs_pc, &ts->tx.prbs); +} + +void ts_init_prbs_rx(struct timeslot_state *ts, unsigned int prbs_offs_rx) +{ + unsigned int prbs_nr = prbs_offs_rx + ts->ofd.priv_nr; + /* initialize the receive-side PRNG for this slot */ + ubit_t ubit[PRBS_LEN*2]; + printf("Selecting PRBS11 #%02u for Rx of TS%02u\n", prbs_nr, ts->ofd.priv_nr); + prbs_for_ts_nr(&ts->rx.prbs, prbs_nr); + prbs_precomp(&ts->rx.prbs_pc[0], &ts->rx.prbs); + osmo_pbit2ubit(ubit, ts->rx.prbs_pc[0].bytes, PRBS_LEN); + /* copy buffer twice back-to-back */ + memcpy(ubit+PRBS_LEN, ubit, PRBS_LEN); + + /* pre-compute bit-shifted versions */ + for (int i = 1; i < ARRAY_SIZE(ts->rx.prbs_pc); i++) { + osmo_ubit2pbit_ext(ts->rx.prbs_pc[i].bytes, 0, ubit, i, PRBS_LEN, 0); + //printf("%d: %s\n", i, osmo_hexdump_nospc(ts->prbs_pc[i].bytes, sizeof(ts->prbs_pc[i].bytes))); + } +} |